1. Field of the Invention
The present invention relates to a new type of thermoplastic cone for root canal filling, having calcium hydroxide as an active ingredient.
2. Description of the Prior Art
An important and frequently performed dental procedure is the filling of root canals of teeth. Typically, such root canals are filled with thermoplastic cones or "points," which are attached with dental cement.
Voids between cones placed in root canals have previously been an inevitable consequence of unevenness in the canal walls and differences in diameter between canals and cones. These voids, left untreated, allow entry of oral fluids into the filled root canal, with a concomitant increased likelihood of failure of the root canal filling. In fact, it is estimated that nearly 60% of failures in endodontic treatments stem from incomplete filling of such voids in root canals.
Because of the exceptional importance of completely filling a root canal, many attempts have been made to assure complete filling. Some of these attempts have been directed to filling technique, and others to the intra-canal medication used during the dental procedure. Still other attempts have been directed to the type of filling material used. Moreover, it is currently standard practice to use dental cement, in addition to the cones, in order to complete the filling. All of these attempts fail, in one way or another, to provide a simple, reproducible, inexpensive, and foolproof solution to the serious problem of incompletely filled root canals, and consequent apical leakage.
U.S. Pat. No. 3,047,408, issued on Jul. 31, 1962, to Emery W. Dougherty describes various dental cement compositions which include calcium hydroxide with zinc oxide, colorants, and various substituted phenols. This patent does not suggest the use of guttapercha and the compositions of this patent are permeable to water.
U.S. Pat. No. 4,240,838, issued on Dec. 23, 1980, to Emil Jandourek suggests that a two paste composition, which includes calcium hydroxide and zinc oxide in a base paste and resin, silica, and pigments in a catalyst paste, may be used to facilitate healing of dental pulp and formation of secondary dentine in dental cavities and linings. This patent does not show the use of guttapercha, and does not indicate the ratios provided by the present invention.
U.S. Pat. No. 4,698,376, issued on Oct. 6, 1987, to Erik Asmussen et al., describes a coating to improve bonding between polymeric materials and collagen-containing materials. This patent does not show the use of guttapercha, rigidifiers or radio-opaque materials, and does not indicate the ratios provided by the present invention.
U.S. Pat. No. 4,740,245, issued on Apr. 26, 1988, to Shunichi Futami et al, describes a composition which includes 12% guttapercha, 8% calcium hydroxide, 70% calcium silicate, 8% paraffin wax, and 2% beeswax, all by weight. This reference additionally shows a guttapercha/zinc oxide composition. Also suggested is the use of synthetic analogs of guttapercha, including trans-1,4-polyisoprene. Additional compounds which may be used with these analogs or components, including calcium hydroxide, are discussed. This patent does not indicate the ratios provided by the present invention, and calcium hydroxide in this patent is used as an inert filler ingredient, rather than as an active ingredient.
U.S. Pat. No. 5,141,560, issued on Aug. 25, 1992, to Combe et al., describes dental cement compositions which may include calcium hydroxide and zinc oxide. This patent does not show the use of guttapercha or rigidifiers, and does not indicate the ratios provided by the present invention.
U.S. Pat. No. 5,238,491, issued on Aug. 2, 1993, to Fumihito Sugihara et al., describes a hardening material comprising calcium phosphate and an acidic hardener. This patent does not show the use of guttapercha, rigidifiers or radio-opaque materials, and does not indicate the ratios provided by the present invention.
British Patent 13,084, issued on Jan. 29, 1903, to Arthur Masur, shows the incorporation of guttapercha into various conventional dental cements. These dental cements include zinc oxide, aluminum oxide, and alkalies. This patent does not indicate the ratios provided by the present invention.
United Kingdom Patent 2 108 131, published on May 11, 1981, invented by Michael Braden, describes a dental cement having zinc oxide and calcium hydroxide, but not guttapercha. This patent does not indicate the ratios provided by the present invention.
Japanese Patent 1030507, issued on Jul. 20, 1984, to Kyocera Corp., suggests a binder for root canal filling that has fifteen to twenty percent calcium hydroxide and an X-ray contrast medium. This patent does not show the use of guttapercha or rigidifiers, and does not indicate the ratios provided by the present invention.
Japanese Patent 1085305, issued on Apr. 30, 1986, to M. Takubo, suggests that a root canal filler comprising calcium hydroxide or calcium oxide, bees wax, and a triglyceride is compatible with guttapercha. This patent does not show the use of rigidifiers or radio-opaque materials, and does not indicate the ratios provided by the present invention.
German patent 137,309, issued on Nov. 12, 1902, to Arthur Masur, suggests a composition that is thirty percent guttapercha and seventy percent zinc. This patent does not show the use of calcium hydroxide, and does not indicate the ratios provided by the present invention.
German Patent 958,148 to Bernard discusses root canal filling compositions which include alcohol or glycerol, zinc oxide, and alkaline earth oxides which upon hydration form calcium hydroxide. This patent does not show the use of guttapercha, and does not indicate the ratios provided by the present invention.
The above-cited patents are incorporated herein by reference. None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.